vImageBlurTest.m

/* Ref: <http://indieambitions.com/idevblogaday/perform-blur-vimage-accelerate-framework-tutorial/> */

- (UIImage *)blurryImage:(UIImage *)image withBlurLevel:(CGFloat)blur {
    if (blur < 0.f || blur > 1.f) {
        blur = 0.5f;
    }
    int boxSize = (int)(blur * 100);
    boxSize = boxSize - (boxSize % 2) + 1;
    
    CGImageRef img = image.CGImage;
    
    vImage_Buffer inBuffer, outBuffer;
    vImage_Error error;
    
    void *pixelBuffer;
    
    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
    
    inBuffer.width = CGImageGetWidth(img);
    inBuffer.height = CGImageGetHeight(img);
    inBuffer.rowBytes = CGImageGetBytesPerRow(img);
    
    inBuffer.data = (void*)CFDataGetBytePtr(inBitmapData);
    
    pixelBuffer = malloc(CGImageGetBytesPerRow(img) * 
                         CGImageGetHeight(img));
    
    if(pixelBuffer == NULL)
        NSLog(@"No pixelbuffer");
    
    outBuffer.data = pixelBuffer;
    outBuffer.width = CGImageGetWidth(img);
    outBuffer.height = CGImageGetHeight(img);
    outBuffer.rowBytes = CGImageGetBytesPerRow(img);
    
    error = vImageBoxConvolve_ARGB8888(&inBuffer, 
                                       &outBuffer, 
                                       NULL, 
                                       0, 
                                       0, 
                                       boxSize, 
                                       boxSize, 
                                       NULL, 
                                       kvImageEdgeExtend);
    
    
    if (error) {
        NSLog(@"error from convolution %ld", error);
    }
    
    CGColorSpaceRef colorSpace = CGImageGetColorSpace(img);
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(img);
    CGContextRef ctx = CGBitmapContextCreate(
                                    outBuffer.data,
                                    outBuffer.width,
                                    outBuffer.height,
                                    8,
                                    outBuffer.rowBytes,
                                    colorSpace,
                                    bitmapInfo);
    CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
    UIImage *returnImage = [UIImage imageWithCGImage:imageRef 
                                               scale:[[UIScreen mainScreen] scale] 
                                         orientation:UIImageOrientationUp];

    //clean up
    CGContextRelease(ctx);
    CGColorSpaceRelease(colorSpace);
    
    free(pixelBuffer);
    CFRelease(inBitmapData);
    
    CGImageRelease(imageRef);
    
    return returnImage;
}